Thirteen adherent human non-lymphocyte cell lines were tested for their susceptibility to infection by the human immunodeficiency virus (HIV). Productive infection could be demonstrated in three of five colorectal carcinoma cell lines examined; the other eight human lines were not infectible. A susceptible colon carcinoma cell line (HT29) as well as normal colonic mucosa was shown to contain a 3.0 kb species of poly(A)+ CD4 RNA, whereas uninfectible colon carcinoma and rhabdomyosarcoma cell lines synthesized no detectable T4 RNA. A persistently infected colon carcinoma cell line was established that continued to produce progeny HIV for nine months. In collaboration with Dr. Heinrich Westphal, NICHD, transgenic mice were constructed that contain the HIV long terminal repeat (LTR) linked to the gene for the bacterial enzyme chloramphenicol acetyltransferase (CAT). Independently derived transgenic animals showed a consistent tissue pattern of high CAT expression in thymus, heart, tail and lens epithelium. When T- lymphocytes from transgenic animals were propagated in the presence of IL-2, a 10-fold increase of CAT activity was observed. This system represents a safe and potentially valuable model for evaluating the effects of cellular and viral transactivators on dormant HIV proviruses.